1. Field of the Invention
The present invention relates to a method of forming a weather strip to be attached around a door opening in a motor vehicle and, more particularly, to a method of forming a corner part of such a weather strip.
2. Description of Related Art
A weather strip to be attached around a door opening of a motor vehicle has a trim portion to be secured to a body panel around the door opening, and a seal portion projecting from an outside wall of the trim portion which is pressed by a peripheral edge of a vehicle door. The weather strip thus arranged is generally formed by integrally extruding the trim portion and seal portion.
To attach the weather strip around the door opening, it is necessary to bend it to conform to the corners of the opening. However, bending the weather strip deforms the cross-sectional shape of the seal portion which degrades the sealing properties thereof. To overcome this problem, the following method has been adopted.
A seal portion of an extruded weather strip is cut off in the part to be attached to a corner of the door opening, and a remaining trim portion of this part is bent to a corner configuration and placed in a mold. Then, a molding material is injected into the mold to form a molded seal portion having a cross-section substantially identical to that of the extruded weather strip onto the remaining trim portion.
FIG. 1 illustrates a trim portion placed in a mold 10. The mold 10 has a cavity 12 having a letter C-shaped cross-section and a corner configuration, which is adapted to form a molded seal portion. A gate 18 and supply passageway 20 provide a flow passageway to the cavity 12 for injecting a molding material thereinto.
A trim portion 14 remaining uncut in a weather strip W is bent and placed in the mold 10. A molding material is injected into the cavity 12 by way of the supply passageway 20 and flows through the gate 18 from the end of the cavity 12 towards a cut edge 22 of a seal portion 24 while diverging rightwards and leftwards, as shown by arrows in FIGS. 1, 2 and 3. Thus, a molded seal portion 26 which is joined to the extruded weather strip W is formed. Thereafter, the mold 10 is opened and a core member 16 is removed.
The above-described conventional method, however, exhibits the problem that unmolded spaces 28 may be generated at angular corners of the molded seal portion 26 due to shortage of the molding material, as shown in FIG. 2. Furthermore, as shown in FIG. 3, wrinkles 30 may be formed around such angular corners due to excess molding material being supplied. These problems result from inevitable variations in the injection amount, injection pressure, viscosity or the like of the molding material. When the weather strip W is attached to a vehicle body, these molding defects 28 and 30 are visible and degrade the appearance quality and sealing properties of the weather strip.